The Medium Range Ordering of Amorphous Alloys: Chemical Short Range Ordring and Bernal Polyhedra

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04210
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Inorganic industrial materials
• Research Institution: Tohoku University
• Principal Investigator: Sugiyama Kazumasa 東北大学, 金属材料研究所, 教授 (40196762)
• Co-Investigator(Kenkyū-buntansha): 有馬 寛 一般財団法人総合科学研究機構(総合科学研究センター(総合科学研究室)及び中性子科学センター(研究開発, 中性子科学センター, 研究員 (60535665)
• Research Collaborator: KAWAMATA TORU
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: amorphous metal / short range ordering / middle range ordering / anomalous scattering / reverse Monte Calro / radial distribution

Outline of Final Research Achievements

In this study, we used the advanced AXS-RMC method to evaluate the medium-range ordering structure of an amorphous alloy that shows a pre-peak signal in the diffraction profile. It was clarified that the clear short-range ordering structures such as icosahedral cluster (TSRO) and/or the strongly binding solute-center model (CSRO), which have been regarded as the origin of pre-peaks in the past, are not essential elements for the appearance of pre-peak signals. And, according to the newly developed CA-Bernal analysis, the identity of pre-peak signal is suggested to be formed by the harmony of the strongly binding Bernal-typed high density domain structure (CMRO) and the non-Bernal-typed low density domain structure (TMRO) inherent in composition and density non-uniformity.

Free Research Field

金属物理化学

Academic Significance and Societal Importance of the Research Achievements

非晶質合金中の中距離領域構造はガラス形成能や機械的特性などの巨視的な材料特性に影響をおよぼす重要な要素であると議論されているが，その詳細は金属分野における未解決問題の１つとなっていた．本研究は，回折プロファイルにプレピークをもつ非晶質合金を研究対象に，研究グループ独自のAXS-RMC法とCN-Bernal解析を駆使して，中距離領域構造の詳細を解明した．溶質元素と溶媒元素の強い結合性に起因する充填密度の大きなBernal型CMROと溶媒元素の希薄な充填密度の低い非Bernal型TMROの協奏は，ランダム系物質の構造を理解するための学術的なブレイクスルーとなると確信している．